In recent years, tremendous progress has been made in developing equipment for electronic data processing such that today high speed reliable hardware is available to the data processing designer. The newly developed electronic components, particularly those using integrated circuits, have greatly increased the capacity of modern electronic data processing equipment to process data. As the speed and capacity of processing has increased, the data storage requirements have also increased. At present several different techniques exist for storing large quantities of digital data including punched cards, punched tape, magnetic tape, magnetic drums, magnetic disc, and magnetic cores. In all of these types of storage, with the exception of magnetic cores and their solid state storage counterparts, a relatively long period of time is required for accessing any particular bit of data.
On the other hand, with random access type memories such as provided with magnetic cores and their semiconductor counterparts, any particular bit or word stored in the memory can be retrieved extremely fast, the time required to read any stored bit of information being only the time required for the electronic circuits to operate. However, increased speed has also resulted in increased costs. As a consequence, considering in general the memories discussed above, the cost per bit of information stored is cheapest with the slowest devices and most expensive with the fastest devices. Accordingly, there has been an effort to develop large capacity memories which are characterized by a large data access time but which are less expensive than magnetic cores and solid state storage configurations.
In this regard, significant interest has developed recently in a class of magnetic devices generally referred to as magnetic domain devices or "magnetic bubbles". These devices are described, for example, in IEEE Transactions on Magnetics, Vol. MAG-5, No. 3 (1969), pp. 544-553, "Application of Orthoferrites to Domain-Wall Devices". These magnetic domain devices are generally planar in configuration and are constructed of materials which have magnetically easy directions which are essentially perpendicular to the plane of the structure. Magnetic properties such as magnetization anisotropy, coercivity, and mobility, are such that the device may be maintained magnetically saturated with magnetization in a direction substantially perpendicular to the plane and that small localized single domain regions of magnetic polarization aligned opposite to the general polarization direction may be supported. Such localized regions which are generally cylindrical in configuration represent binary memory bits. Interest in these devices in large part is based on the high density that can be obtained and the ability of the cylindrical magnetic domains to be independent of the boundary of the magnetic material in the plane in which it is formed and hence they are capable of moving anywhere in the plane of the magnetic material to effect various data processing operations.
A magnetic domain can be manipulated by programming currents through a pattern of conductors positioned adjacent the magnetic material or by varying the surrounding magnetic field. As an example, the magnetic domains may be formed in thin platelets having uniaxial anisotropy with the easy magnetic axis perpendicular to the plate comprising such material as rare earth orthoferrites, rare earth aluminum and gallium substituted iron garnets and rare earth cobalt or iron amorphous alloys. Since the magnetic bubbles can be propagated, erased, replicated and manipulated to form data processing operations and their presence and absence detected, these bubbles may be utilized to perform the primary functions vital to memory operation.
Many structural organizations of operable magnetic domains have been disclosed in the literature. One of the most popular is the major-minor memory organization disclosed in U.S. Pat. No. 3,618,054. The major-minor loop memory organization as well as its implementation and operation is well known in the art. The major-minor loop organization includes a closed major loop which typically is established by an arrangement of T-bar permalloy circuits on, for example, a rare earth orthoferrite platelet. The magnetic domains are propagated around the loop by in-plane rotating magnetic field action. The major loop is generally elongated to permit a number of minor loops to be aligned along side it. Two way transfer gates permit the transfer of magnetic domains from the minor loop to the major loop and from the major loop to a minor loop. Further access to the major loop is achieved by a detect and read connection thereto, by a separate write connection, and by an erase connection.
The organization above described permits a synchronized domain pattern since propagation in the loops is synchronous with the rotation of the in-plane field. That is, parallel transfer of data domains from a plurality of minor loops may be made simultaneously to the major loop. Moreover, a plurality of data chips, each with a major loop and a plurality of associated minor loops, may be treated together. It is common to arrange such data chips in rows and then even to stack rows of data chips in time multiplexed layers to achieve complex memory structures, the data domains in all the loops and all the chips being synchronized with in-plane rotations.
Typically all of the minor loops in the chip, upon command, transfer in parallel the bubbles from their corresponding positions to the major loop. The bubbles are then serially detected as they are propagated past a read position. New data may also be inserted at a write position for parallel transfer back into the minor loops at an appropriate time later (when major loop magnetic domain propagation aligns the data for transfer). This operation may be characterized as a single page transfer of data, i.e. only one page of data in the major loop at any one time.
Simultaneous reading/writing of data into a grouping of related major loops gives the capacity of treating related magnetic domains as digital or other coded words. Time multiplexed groups of data chips permit reading and writing of data in a time sharing fashion to permit an overall memory data rate greater than that permitted by magnetic domain propagation in a single chip.
The major loop propagation path in the major-minor loop organization structure is large enough to hold more than one page of bubble information. A page is defined by a simultaneous transfer out of a bit from the same virtual position of every minor loop onto the major propagation path. However, it has heretofore been a general practice in the art to provide a single page of information within the bubble major propagation path at any one time as described above.
In order to initiate the bubble functions, as for example reading and writing from the bubble chip, it is necessary to have a controlling mechanism to filter command signals from the bubble user to the bubble memory device to enable the necessary bubble functions. The controllers used heretofore have been mainly of an unsophisticated type to simply initiate bubble functions. There is a distinct need for a more sophisticated controller in combination with a magnetic bubble memory device to perform more adequately as an interface with a user system. There is also the need that a controller be sophisticated enough to be able to handle magnetic bubble memory device replacement along with providing an efficient means of function timing to enable the chip to perform at its optimum level.